Organization and Information Support of Expert Reviews of I&C Systems Modernization at NPP of Ukraine - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 371

example, in GOST, 1992,b, DSTU, 1999, USNRC,
2010) regulatory documents. At the moment, one
of the most known models for NPP I&C systems
is V-model of LC (IAEA, 2002).
It should be mentioned that in Ukraine in most
cases the point is not in the implementation of
fundamentally new I&C systems or systems on
new power units (such cases are relatively un-
common), but in general about modernization of
current, obsolete and physically ageing NPP I&C
systems. Therefore one of the main regulatory
documents that define LC stages of I&C systems
is NP 306.2.106 “Requirements for modification
of nuclear plants and procedure for their safety
assessment.”
According to NP, 2005,b, when changes occur
in the design, structure of safety important systems
(including I&C systems), or their characteristics
and software, the operator develops and agrees
technical decisions for specified stages of modi-
fication with the regulatory authority.
So, LC stages of the NPP I&C systems are
connected with making proper technical decisions
by the operator or with releasing other documents,
substantiating safety of the NPP I&C systems
(requirement specification, engineering design
etc.). Technical decisions are approved by operator
management, agreed with the design organization
(as required), and submitted to the regulatory au-
thority for approval. Each next stage of modifica-
tion at NPP can be started only after approval of
a proper technical decision. The operator should
provide required documentation sufficient for
consideration and assessment of a proper techni-
cal decision by the regulatory authority in time.
On the basis of the analysis NP, 2005,b six
main life cycle stages of the NPP I&C system
can be marked out:

• Development of technical requirements for
modernization (creation) of the NPP I&C
system;
• Design, production and testing of compo-
nents of the I&C system at the enterprise;
• Assembling and commissioning of the
I&C system at NPP;

• Putting the i&c system into trial operation

at npp;

• Putting the I&C system into stationary op-

eration at NPP.

Each life cycle stage is conformed to a specific
set of documents released by the I&C developer,
design organization or NPP for safety validation
of implemented (modified) I&C system.
Let us consider these stages sequentially.

Stage 1: Development of modification concept of
the NPP I&C systems (or implementation
of the new NPP I&C).

At this stage, the operator develops a concep-
tual decision of NPP modification that is agreed
by the regulatory authority before starting any
operations related to NPP modification.
The conceptual decision should contain the
following information:

• Determination of the modiication object;
• Purpose of modiication, substantiation
of its necessity with determination of
safety deiciencies or deviations from re-
quirements of safety standards and rules,
which are eliminated by the suggested
modiication;
• Short description of modiication;
• Assessment of modiication efects on safe-
ty of NPP, its personnel and environment;

• Development of a modiication concept of
the NPP I&C system (or implementation
of the new NPP I&C system);

• Suggestions regarding determination of

safety class and classiication indicator of
the modiication object;